So, after all, nothing happened? Or market just slow reacting?
Probably not. Market manipulation is harder than it sounds. CME limits what an entity/group/person can hold, which makes it almost unprofitable given the cost of manipulation.
On the other hand, this futures expiration dip is more of a fud than an actual event. Price fluctuates too much not because of actual manipulation, but because people expects and are afraid of that manipulation.
See, nothing happened. As Maveth says, CME on its own cannot really do much, so this was nothing much to do with futures in the first place. As people keep reminding anyway, none of the contracts actually involve Bitcoin. It is just a bunch of people betting on whether the price goes up or down.
As yes, the actual event does not cause price fluctuations, rather people react in anticipation of news, and events. They either panic and sell out of fear and uncertainty, or buy in the fear of missing out, this is the herd mentality famous in trading.